Modern aircraft may utilize one or more gas turbine engines enclosed within a nacelle. The nacelle may comprise a cascade-type thrust reverser. The thrust reverser may include a translating sleeve, a cascade array, and a thrust reverser actuation system (“TRAS”) actuator. The TRAS actuator may pass through the aft cascade ring of the cascade array.
The design of the pass through the aft cascade ring is influenced by several competing factors. The TRAS actuator may benefit from a pass-through in the aft cascade ring that is as large as possible so that the TRAS actuator avoids contact with the aft cascade ring. If the actuator contacts the aft cascade ring the contact will result in side loads to the actuator which may develop into damage which may cause actuator leakage. On the other hand, the aft cascade ring is a structural component and may benefit from the smallest possible pass-through in order to maintain maximum cross-sectional area for increased structural strength.
Tolerance stack-ups are also a factor and compound the problem by requiring additional clearance between the TRAS actuator and the aft cascade ring. It may be helpful to provide a damper between the aft cascade ring which provides vibration damping under normal conditions. In addition, as nacelle loft lines continue to become more constrictive, the space constraints become narrower, and the actuator and cascades must be fit into a compact space.
Some existing systems may include large gaps between the actuator and the aft cascade ring, with relatively hard bumpers arranged between the actuator and the ring. The bumpers ensure that there is no metal-metal contact if the actuator deflects enough to contact the ring (it will contact the non-metallic bumper instead). A large gap ensures the bumper does not apply any preload to the actuator which can cause premature wear. However, the gap also results in no ability to provide a damping resistance load to damp normal vibrations of the actuator. Other existing systems may allow a small pass-through in the aft cascade ring, and provide a damper which is closely positioned relative to, or is in constant contact with the actuator. The closely positioned damper provides vibration damping during normal operation of the actuator. The mounting of the damper may be adjustable so that it does not exert a preload on the actuator, but in reality the adjustment to a zero preload position is difficult to achieve and often results in a preload anyway.